This one is a little bit of a cheat, since strictly speaking it’s not just one book as Anne O’Brien’s The Scandalous Duchess and Anya Seton’s Katherine are just as interesting. But it’s all the same story – girl meets duke, duke is dynastically married, duke and girl have four children together anyway and their love partly causes the Peasants’ Revolt but despite everything duke loves girl and they manage to get married. I will happily drop a half hour long spiel about amazing it is should anybody show the slightest chance of being interested. Be warned. I was amazed by this story when I first read it in Katherine, delighted to discover that it really did happen in Alison Weir’s non-fiction Katherine Swynford and then I fell in love all over again in The Scandalous Duchess. John of Gaunt is quite literally the hottest man in history.